Pixel perfect camera in SDL2

pixelperfect.c

#include "SDL.h"
#include "stb/stb_image.h"

#define CAMERA_BORDER 1

typedef struct {
    SDL_Renderer *renderer;
    SDL_Texture *target;

    int width;
    int height;

    int target_width;
    int target_height;

    float x, y;
} Camera;

typedef struct {
    SDL_Texture *texture;
    int width;
    int height;

    float x, y;
} Sprite;

Camera make_camera(SDL_Renderer *renderer, int width, int height) {
    Camera camera = {
        .renderer = renderer,
        .x = 0,
        .y = 0,
        .width = width,
        .height = height,
        .target_width = width + CAMERA_BORDER * 2,
        .target_height = height + CAMERA_BORDER * 2,
    };
    camera.target = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA32, SDL_TEXTUREACCESS_TARGET,
                                      camera.target_width, camera.target_height);
    SDL_assert(camera.target);
    SDL_SetTextureBlendMode(camera.target, SDL_BLENDMODE_BLEND);

    return camera;
}

Sprite load_sprite(SDL_Renderer *renderer, const char *filename) {
    Sprite sprite = {0};
    int channels;
    stbi_uc *image = stbi_load(filename, &sprite.width, &sprite.height, &channels, STBI_default);
    int fmt = channels == 3 ? SDL_PIXELFORMAT_RGB24 : SDL_PIXELFORMAT_RGBA32;

    int pitch = sprite.width * channels;
    sprite.texture = SDL_CreateTexture(renderer, fmt, SDL_TEXTUREACCESS_STATIC, sprite.width, sprite.height);
    SDL_UpdateTexture(sprite.texture, NULL, (const void *)image, pitch);

    stbi_image_free(image);
    return sprite;
}

int main(int argc, char **argv) {
    const int Window_Width = 640;
    const int Window_Height = 360;

    //
    // Window creation
    //
    SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS);
    SDL_Window *window = SDL_CreateWindow("Pixel Perfect", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, Window_Width, Window_Height, 0);
    SDL_assert(window);

    SDL_SetHint(SDL_HINT_RENDER_BATCHING, "1");
    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    SDL_assert(renderer);

    //
    // Init
    //
    Sprite sprite = load_sprite(renderer, "sprite.png");
    Camera camera = make_camera(renderer, 32, 18);
    int direction = 0;

    //
    // Main loop
    //
    SDL_Event e;
    while (1) {
        while (SDL_PollEvent(&e)) {
            switch (e.type) {
            case SDL_QUIT:
                goto exit;
            case SDL_KEYDOWN:
                if (e.key.keysym.sym == SDLK_SPACE) {
                    if (direction == 0)
                        direction = 1;
                    else
                        direction *= -1;
                }
                break;
            default:
                break;
            }
        }
        camera.y += 0.05f * direction;

        //
        // Camera target
        //
        SDL_SetRenderTarget(renderer, camera.target);
        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0xFF);
        SDL_RenderClear(renderer);

        //
        // Draw Sprite
        //
        SDL_Rect sprite_rect;
        sprite_rect.x = (int)(sprite.x - camera.x) + CAMERA_BORDER;
        sprite_rect.y = (int)(sprite.y - camera.y) + CAMERA_BORDER;
        sprite_rect.w = sprite.width;
        sprite_rect.h = sprite.height;

        SDL_RenderCopy(renderer, sprite.texture, NULL, &sprite_rect);

        //
        // Screen target
        //
        SDL_SetRenderTarget(renderer, NULL);
        SDL_SetRenderDrawColor(renderer, 0x00, 0xFF, 0xFF, 0xFF);
        SDL_RenderClear(renderer);

        //
        // Draw camera texture
        //
        float pixel_h = (float)Window_Height / camera.height;
        float correction_x = (int)camera.x - camera.x;
        float correction_y = (int)camera.y - camera.y;

        SDL_Rect dst;
        dst.x = correction_x * pixel_h - pixel_h * CAMERA_BORDER;
        dst.y = correction_y * pixel_h - pixel_h * CAMERA_BORDER;
        dst.w = camera.target_width * pixel_h;
        dst.h = camera.target_height * pixel_h;

        SDL_RenderCopy(renderer, camera.target, NULL, &dst);
        SDL_RenderPresent(renderer);
    }

exit:
    SDL_DestroyRenderer(renderer);
    SDL_Quit();
    return 0;
}